Figure 1. Root anatomical traits along five orders for five species.

Root diameter, stele diameter and cortex thickness (A), and stele to root diameter ratio (B) for the first five root orders in five species. (A) Root and stele diameter are indicated by open circle and closed circle respectively, and cortex thickness are shown by grey square. Error bars represent one standard error of the mean. Significant difference (P<0.05) for a trait among root orders within individual species is indicated by different lower or upper case letters. See Table 1 for species abbreviations.